The present invention is related to a method and a device for detecting, in a volume of air at a given temperature, the presence of steam at the given temperature.
The present invention is also related to the application of this method and of this device, on the one hand, to the implementation of steam generators, preferably operating at atmospheric pressure, in order to provide them with a quasi-instantaneous response and, on the other hand, to checking the steam supplied by a steam generator to steam cooking ovens under atmospheric pressure.
The present invention is also related to a method and a device adapted to determine the percentage of steam, at a given temperature, that is possibly contained in an air mask at the given temperature.
Steam is used in numerous applications, both household as well as artistic and industrial, where it is necessary to obtain a specific detection of steam, (i.e., distinguishing steam at a given temperature from air at the same temperature). Such means can, for example, be used to supervise adequate and constant filling of steam in an enclosure, which may or may not have a thermostat, or yet again, for example, to detect the start of effective steam production of a steam generator, after a preheating period, or yet again, for example, to indicate any abrupt eruption of steam in a passage, for example, for safety reasons.
It is impossible to use a temperature sensor with a fixed post, to distinguish steam from air in a traditional manner because it is precisely the specific function of such sensors to indicate temperature, regardless of the nature of the gas.
It is possible, inversely, to this end, to use one of the numerous apparatuses or devices for measuring the degree of humidity of a gas, that are available commercially. These apparatuses and devices, mainly hygrometers and psychrometers use varied physical principles, namely expansion of air, changing the capacity of a hygroscopic polymer having a high dielectric constant, measurement of electrical resistivity, the temperature difference between a dry bulb and a moist bulb, cooling and analysis of dew point, etc. These techniques can provide the value of the percentage of humidity of a material with precision, and most of them, of a gas.
However, currently available devices, that provide more than just steam detection are relatively expensive and sophisticated because they provide a value close to the degree of humidity. Besides, the majority of hygrometers and psychrometers only function at relatively low temperatures, generally below 60.degree. C., and only the most expensive apparatuses function correctly above 100.degree. C. Certain devices, such as those implementing the technique of dry bulbs and moist bulbs, require that the apparatus be constantly re-supplied with a quantity of water that corresponds exactly to the evaporated quantity, and are thus delicate to implement.
When the above mentioned applications include establishing a steam flow, one could envision detecting such flow by means of gaseous flow measurement apparatuses, such as debitmeters. However, these measurement devices do not distinguish between air and steam, and do not therefore enable a specific detection of a steam flow, as opposed to an air flow.
We are therefore unaware of detection means specifically for steam, which are simple, strong, easy to implement and inexpensive.